1. Field of Invention
The present invention relates to a method of controlling a hill-start assist control (HAC) operation when an engine is restarted in a vehicle which includes an idle stop and go (ISG) system for an automatic transmission and an HAC system.
2. Description of Related Art
The ISG system is an engine control system that has a function of automatically turning off an engine of a vehicle under a predetermined condition, for example, when the engine maintains an idle state during a predetermined time period after the vehicle stops, and then automatically turning on the engine when restarting is required, so as to make normal driving possible.
In the past, the ISG system was applied to only manual transmissions. However, recently, the ISG system is applicable to vehicles with automatic transmissions. In a case of an ISG system installed in a vehicle with an automatic transmission, in a stop state, the vehicle is automatically restarted in a state in which the transmission is in the D stage. That is, a vehicle with an ISG system for an automatic transmission is automatically restarted in a state in which the transmission is in the D stage, regardless of the will of a driver, unlike an existing ISG for a manual transmission.
In the vehicle with the ISG system for an automatic transmission, the engine is automatically restarted in a state in which the transmission is in the D stage, regardless of the will of a driver, unlike an existing ISG for a manual transmission. Therefore, during the restarting, there is a danger that the vehicle moves forward (sudden acceleration or the like), and the vehicle may vibrate back and forth to make the driver feel uncomfortable (a reduction in driveability).
In order to solve the problems, there have been efforts to reduce a feeling of discomfort against the vehicle with the ISG system for an automatic transmission by operating an HAC system during a predetermined time period after starting the engine. However, since the restarting state of the engine varies according to temperature, pressure, the property of fuel, and the like, it is impossible to provide a constant feeling of driving to the drive. Further, since the characteristics of the HAC system also variously change according to the fluid-pressure formation characteristic of a brake system before the HAC system is operated, the degree of wear/aging of a friction material, and the like, control different from an existing purpose is often performed.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.